合成路线1

The intermediate (XXXIII) has been obtained as follows: The silylation of the OH group of (2S,3R,4S)-2,4-dimethyl-1-(tert-butyldimethylsilyloxy)-5-hexen-3-ol (XVII) with Tbdms-OTf gives the bis-silyl ether (XVIII), which is ozonolyzed with O3 to yield the aldehyde (XIX). The condensation of (XIX) with the phosphonate (XX) by means of KHMDS affords the methyl heptenoate (XXI), which is reduced with LiAlH4 to the carbinol (XXII). The esterification of (XXII) with pivaloyl chloride and pyridine affords the pivaloyl ester (XXIII), which is selectively desilylated with HF and pyridine to provide the primary alcohol (XXIV). The Swern oxidation of (XXIV) gives the aldehyde (XXV), which is condensed with the phosphonate (XXVI) to yield the terminal acetylene derivative (XXVII). Iodination of (XXVII) with I2 and morpholine affords the iodoacetylene (XXVIII), which is condensed with the already reported acetaldehyde intermediate (XVI) by means of NiCl2/CuCl2 to provide the acetylenic alcohol (XXIX). The reduction of the triple bond of (XXIX) with H2 over Pd/C gives the corresponding allyl alcohol derivative (XXX), which is silylated with Tbdms-OTf to the trisilylated compound (XXXI). Elimination of the pivaloyl protecting group of (XXXI) by means of DIBAL yields the primary alcohol (XXXII), which is treated first with MsCl and TEA and then with LiBr to furnish the target bromoderivative intermediate (XXXIII).